TIMESTAMPDIFFDAY

TIMESTAMPDIFFDAY is a function commonly found in database systems and programming languages used to calculate the difference between two datetime values, specifically expressing the result in whole days. This function is distinct from those that might return fractional days or a more detailed breakdown of the time difference.

The typical syntax involves providing two datetime arguments. The first argument is usually the later datetime, and the second is the earlier datetime. The function then returns an integer representing the number of full 24-hour periods that have elapsed between these two points in time. For example, if the first datetime is '2023-10-27 10:00:00' and the second is '2023-10-25 08:00:00', TIMESTAMPDIFFDAY would return 2, as two full days have passed. Hours, minutes, and seconds that do not constitute a full day are truncated in the result.

This function is particularly useful for tasks such as calculating the number of days an event has been active, determining age in whole years (by calculating days and dividing by 365.25, though specific functions for years are often preferred), or setting deadlines based on a number of days from a starting date. Its simplicity makes it a go-to for straightforward day-count calculations, avoiding the complexity of handling time components when only the day difference is relevant.